What is the most likely cause of wireless connectivity issues occurring near the parking lot of a building?

The most likely cause of wireless connectivity issues occurring near the parking lot of a building is the possibility of an external access point engaging in an evil-twin attack. In this scenario, an attacker sets up a rogue wireless access point that masquerades as a legitimate one, straying unsuspecting users away from the genuine access point. As users attempt to connect to what they believe is the legitimate network, they might experience disrupted connectivity or even compromised data due to the malicious nature of the evil twin setup.

This situation specifically explains why users in proximity to the parking lot may experience connection problems, as the rogue access point can create interference or draw traffic away from the authorized access point, leading to instability and lack of service for users trying to connect.

While the other options touch on different connectivity issues, they do not directly address the specific context of external interference or malicious activity that is likely affecting users in that particular area. Signal strength adjustments, expired certificates, or VLAN configurations may impact connectivity but would not typically arise specifically in a defined outdoor area like a parking lot as a direct result of an external threat.